The San Antonio Heart Study is a comprehensive epidemiological study of "diabetic pattern" cardiovascuar risk factors (glucose intolerance, obesity, hypertriglyceridemia and low levels of alpha-lipoprotein) in Mexican American and Anglo residents of San Antonio. We are testing the hypothesis that as Mexican Americans acculturate to "mainstream" U.S. lifestyle they will gradually lose their excess of diabetic pattern risk factors. We are also evaluating a possible genetic basis for ethnic differences in risk factors. Our experimental design is to study random samples of Mexican Americans and Anglos in three socioculturally distinct target areas throughout San Antonio. These target areas are: a low income, highly traditional barrio; a middle income bicultural area; and an affluent suburban area. Thus far we have studied 1039 subjects (285 in the bicultural area, 642 in the suburbs and 112 in the barrio). "Diabetic pattern" risk factors are markedly lower in the suburbs in both ethnic groups. Residual ethnic differences, however, still persist even within target areas.